Periodicity of western spruce budworm in Southern British Columbia, Canada

Comparative ecology of conifer-feeding spruce budworms (Lepidoptera: Tortricidae)

“…Mean outbreak duration for C. fumiferana is approximately nine years in eastern and 12 years in western Canada, but varies from a few to as many as 25 years in all regions (Table 1; Candau et al 1998;Gray et al 2000). The duration of western spruce budworm outbreaks is similar to spruce budworm outbreaks Lynch 1989, 1993;Flower et al 2014) although apparently is shorter in the northern portions of the range where outbreaks usually last less than 10 years and often no more than four years (Table 1; Johnson and Denton 1975;Maclauchlan et al 2006;Alfaro et al 2014). …”

“…Overall the historical record for spruce budworm suggests a low frequency periodicity synchronised over a wide geographic range. Evidence of outbreaks in western spruce budworm has been reconstructed from tree rings in New Mexico, United States of America (Swetnam and Lynch 1993), Colorado, United States of America (Swetnam and Lynch 1989;Ryerson et al 2003), Pacific Northwest, United States of America (Flower et al 2014), and British Columbia, Canada (Campbell et al 2006;Alfaro et al 2014). Here, too, there is evidence of regional-level outbreaks that share large-scale patterns for several centuries.…”

Impacts of insect outbreaks on tree mortality, productivity, and stand development

“…In contrast, in British Columbia, spruce budworm outbreaks occurred on average every 26 years, with five to six outbreaks in the past century in the northern regions of the district, while southern regions experienced between zero (the most southern sites) and four outbreaks (Burleigh et al 2002). Western spruce budworm in southern British Columbia had a mean return interval of 28 years (95% confidence interval 21-35 years), with three to four outbreaks per century since the 1800s (Alfaro et al 2014a). …”

Changing paradigms in the management of forest insect disturbances

“…For example, extensive dendroentomology work has been completed to reconstruct the long-term history of C. fumiferana in the boreal forest of eastern Canada (e.g., Boulanger et al 2012). Alfaro et al (2014) reconstructed the history of western spruce budworm for the last 400 years in central British Columbia and calculated a return interval that averaged 28 years, with mean outbreak duration of nine years (Fig. 1).…”